Your post is somewhat confusing. You said "mountaineering" - i.e. if you're doing techincal winter climbing, then you're probably talking a plastic shell climbing boot. I.E as is made by Scarpa, Koflach, etc. I no experience with those.

If you are looking for a *winter* boot suitable for hiking in in very cold weather. Most people (including myself) who do this use some kind of mukluk or pac boot type. My personal favorite, because they work, and are cheap, and easy to get where I live is the Canadian Army issue mukluk -but you can
do pretty will with clones made by Sorel or kamik, etc.

At least with mine, I have two sets of the felt liners (so I can alternate and ensure I have a dry set), and I use a plastic waffle weave footbed, topped with a thermal
footbed underneath the liner (between the liner and the bottom of theboot). With this I don't have any problem with my feet standing around in -40..

Let's see. what I have are:
Canadian Forces Mukluks
(shop around to get a deal, because they aren't that hard to find)

I know lots of people who swear by stegers:
http://shop.mukluks.com/prodinfo.asp?number=AR-R&title=Arctic with Ribbon Mukluks

And these look good:
http://www.empirecanvasworks.com/truenorthboots.htm

However these are *NOT* for mountaineering - i.e climbing.